Communication method and system in handover carrying NSSAI, and corresponding core network device

ABSTRACT

Embodiments of the present invention provide a communication method, an access network device, a core network device, and user equipment. One example method includes: sending, by a core network device, a handover request to an access network device, wherein the handover request comprises first information, and the first information comprises an identifier of allowed network slice selection assistance information (NSSAI); and sending, by the access network device, a handover request acknowledgement to the core network device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/503,278, filed on Jul. 3, 2019, which is a continuation ofInternational Application No. PCT/CN2018/071271, filed on Jan. 4, 2018,which claims priority to Chinese Patent Application No. 201710010762.3,filed on Jan. 6, 2017. The disclosures of the aforementionedapplications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present invention relate to the communications field,and more specifically, to a communication method, an access networkdevice, a core network device, and user equipment.

BACKGROUND

With rapid development of wireless communications technologies, a 5thgeneration (5th Generation, 5G for short) wireless communicationstechnology currently has become a hot topic in the art. 5G supports avariety of application requirements, including: support of an accesscapability with higher-speed experience and higher bandwidth,information exchange with a lower latency and high reliability, accessand management of massive machine type communication devices with lowcosts, and the like. In addition, 5G supports various vertical industryapplication scenarios, such as the Internet of Vehicles, emergencycommunications, and the industrial Internet. Due to these performancerequirements and application scenarios of 5G, a 5G network needs tobetter meet a particular requirement of a user, and a customizationcapability of the 5G network needs to be further improved.

Therefore, an important concept, namely, a network slice, is introducedin 5G. An operator network may include a critical machine typecommunication (Critical Machine Type Communication, Critical MTC forshort) network slice, a massive machine type communication (MassiveMachine Type Communication, Massive MTC for short) network slice, and amobile broadband (Mobile Broad Band, MBB for short) network slice.

When network slice instances are deployed in a network system, userequipment cannot aware these network slice instances.

SUMMARY

Embodiments of the present invention provide a communication method, anaccess network device, a core network device, and user equipment, sothat the user equipment can aware a network slice instance.

According to a first aspect, a communication method is provided,including the following steps: receiving, by an access network device,first information sent by a core network device, where the firstinformation includes information about a cell that supports a networkslice instance and that allows or does not allow user equipment toaccess; and sending, by the access network device, the first informationto the user equipment. In the foregoing process, the user equipment mayobtain the information about a cell that supports a network sliceinstance and that allows or does not allow the user equipment to access,to aware the network slice instance. In addition, dedicated signaling isused in the foregoing process, so that signaling overheads can bereduced. Each user equipment supports a different network sliceinstance. As such, effective information can be provided by usingdedicated signaling and based on a network slice instance supported byeach UE, so that customization processing can be implemented on the userequipment. In addition, the user equipment does not need to aware thenetwork slice instance due to an access failure, so that unnecessaryrequests such as a connection establishment request and a sessionrequest of the UE are avoided.

According to a second aspect, a communication method is provided,including the following steps: receiving, by user equipment, firstinformation sent by an access network device, where the firstinformation includes information about a cell that supports a networkslice instance and that allows or does not allow the user equipment toaccess; and storing, by the user equipment, the first information.

With reference to the second aspect, in a possible design, thecommunication method further includes: selecting, by the user equipmentbased on the first information, a cell that supports a network sliceinstance and that allows the user equipment to access, to camp on.

With reference to the second aspect, in a possible design, thecommunication method further includes: determining, by the userequipment based on the first information, to perform data transmissionin a cell that supports a network slice instance and that allows theuser equipment to access.

With reference to the second aspect, in a possible design, thecommunication method further includes: attaching, by the user equipmentbased on the first information, to a cell that supports a network sliceinstance and that allows the user equipment to access, to trigger aservice request.

According to a third aspect, a communication method is provided,including the following steps: sending, by a core network device, aninitial context setup request to an access network device, where theinitial context setup request includes first information, and the firstinformation includes information about a cell that supports a networkslice instance and that allows or does not allow user equipment toaccess; and receiving, by the core network device, an initial contextsetup request complete message.

According to a fourth aspect, an access network device is provided,including: a transceiver; a memory, configured to store an instruction;and a processor. The processor is separately connected to the memory andthe transceiver, and is configured to execute the instruction stored inthe memory, to perform the following steps when executing theinstruction: receiving, by using the transceiver, first information sentby a core network device, where the first information includesinformation about a cell that supports a network slice instance and thatallows or does not allow user equipment to access; and sending the firstinformation to the user equipment by using the transceiver.

According to a fifth aspect, user equipment is provided, including: atransceiver; a memory, configured to store an instruction; and aprocessor. The processor is separately connected to the memory and thetransceiver, and is configured to execute the instruction stored in thememory, to perform the following steps when executing the instruction:receiving, by using the transceiver, first information sent by an accessnetwork device, where the first information includes information about acell that supports a network slice instance and that allows or does notallow the user equipment to access; and storing the first information byusing the memory.

According to a sixth aspect, a core network device is provided,including: a transceiver; a memory, configured to store an instruction;and a processor. The processor is separately connected to the memory andthe transceiver, and is configured to execute the instruction stored inthe memory, to perform the following steps when executing theinstruction: sending an initial context setup request by using thetransceiver, where the initial context setup request includes firstinformation, and the first information includes information about a cellthat supports a network slice instance and that allows or does not allowuser equipment to access; and receiving an initial context setup requestcomplete message by using the transceiver.

According to a seventh aspect, a communication method is provided,including the following steps: receiving, by an access network device,first information sent by a core network device, where the firstinformation includes information about a tracking area that supports anetwork slice instance and that allows or does not allow user equipmentto access; and sending, by the access network device, the firstinformation to the user equipment.

According to an eighth aspect, a communication method is provided,including the following steps: receiving, by user equipment, firstinformation sent by an access network device, where the firstinformation includes information about a tracking area that supports anetwork slice instance and that allows or does not allow the userequipment to access; and storing, by the user equipment, the firstinformation.

According to a ninth aspect, a communication method is provided,including the following steps: sending, by a core network device, aninitial context setup request to an access network device, where theinitial context setup request includes first information, and the firstinformation includes information about a tracking area that supports anetwork slice instance and that allows or does not allow user equipmentto access; and receiving, by the core network device, an initial contextsetup request complete message.

According to a tenth aspect, an access network device is provided,including: a transceiver; a memory, configured to store an instruction;and a processor. The processor is separately connected to the memory andthe transceiver, and is configured to execute the instruction stored inthe memory, to perform the following steps when executing theinstruction: receiving, by using the transceiver, first information sentby a core network device, where the first information includesinformation about a tracking area that supports a network slice instanceand that allows or does not allow user equipment to access; and sendingthe first information to the user equipment by using the transceiver.

According to an eleventh aspect, user equipment is provided, including:a transceiver; a memory, configured to store an instruction; and aprocessor. The processor is separately connected to the memory and thetransceiver, and is configured to execute the instruction stored in thememory, to perform the following steps when executing the instruction:receiving, by using the transceiver, first information sent by an accessnetwork device, where the first information includes information about atracking area that supports a network slice instance and that allows ordoes not allow the user equipment to access; and storing the firstinformation by using the memory.

According to a twelfth aspect, a core network device is provided,including: a transceiver; a memory, configured to store an instruction;and a processor. The processor is separately connected to the memory andthe transceiver, and is configured to execute the instruction stored inthe memory, to perform the following steps when executing theinstruction: sending an initial context setup request by using thetransceiver, where the initial context setup request includes firstinformation, and the first information includes information about atracking area that supports a network slice instance and that allows ordoes not allow user equipment to access; and receiving an initialcontext setup request complete message by using the transceiver.

With reference to any one of the foregoing aspects, in a possibledesign, the first information further includes information indicatingthat a network slice instance accessed by the user equipment is allowedto be switched to another network slice instance. Therefore, when anetwork slice instance is deployed by area, based on the informationindicating that a network slice instance accessed by the user equipmentis allowed to be switched to another network slice instance, continuityof an original data flow of the user equipment can be guaranteed as muchas possible, and traffic flow interruption is avoided.

With reference to any one of the foregoing aspects, in a possibledesign, the network slice instance is determined by using network sliceselection assistance information.

With reference to any one of the foregoing aspects, in a possibledesign, the network slice instance is determined by using a networkslice instance identifier.

With reference to any one of the foregoing aspects, in a possibledesign, the access network device determines, by using the firstinformation, a target access network device to which the user equipmentis handed over.

According to another aspect of this application, a computer readablestorage medium is provided. The computer readable storage medium storesan instruction. When the instruction runs on a computer, the computerexecutes the methods in the foregoing aspects.

According to another aspect of this application, a computer programproduct that includes an instruction is provided. When the instructionruns on a computer, the computer executes the methods in the foregoingaspects.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic architectural diagram of a network systemaccording to an embodiment of the present invention:

FIG. 1B is a schematic diagram in which a network slice is deployed byarea;

FIG. 1C is another schematic diagram in which a network slice isdeployed by area;

FIG. 2 is a schematic interaction diagram of a service request when userequipment is switched from an idle mode to a connected mode according toanother embodiment of the present invention:

FIG. 3 is a schematic interaction diagram in which user equipmentaccesses a network according to another embodiment of the presentinvention;

FIG. 4A is a schematic diagram of a mobility scenario according to anembodiment of the present invention;

FIG. 4B is a schematic interaction diagram in which user equipment ishanded over according to another embodiment of the present invention:

FIG. 5 is a schematic interaction diagram in which user equipment ishanded over according to another embodiment of the present invention;

FIG. 6 is a schematic interaction diagram of state transition ofinactive user equipment according to another embodiment of the presentinvention:

FIG. 7 is a schematic diagram of a tracking area update procedure ofuser equipment according to another embodiment of the present invention;

FIG. 8 is a schematic diagram of an access network device according toan embodiment of the present invention;

FIG. 9 is a schematic diagram of user equipment according to anembodiment of the present invention; and

FIG. 10 is a schematic diagram of a core network device according to anembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes the technical solutions in the embodiments ofthe present invention with reference to the accompanying drawings in theembodiments of the present invention.

It should be understood that the technical solutions in the embodimentsof the present invention may be applied to various communicationssystems, such as a Global System for Mobile Communications (GlobalSystem for Mobile Communications, GSM), a Code Division Multiple Access(Code Division Multiple Access, CDMA) system, a Wideband Code DivisionMultiple Access (Wideband Code Division Multiple Access, WCDMA) system,a general packet radio service (General Packet Radio Service, GPRS), aLong Term Evolution (Long Term Evolution. LTE) system, an LTE frequencydivision duplex (Frequency Division Duplex, FDD) system, an LTE timedivision duplex (Time Division Duplex, TDD) system. Universal MobileTelecommunications System (Universal Mobile Telecommunications System,UMTS), a Worldwide Interoperability for Microwave Access (WorldwideInteroperability for Microwave Access, WiMAX) communications system, anda future 5G communications system.

The embodiments of the present invention relate to a network slicingtechnology. The network slicing technology logically abstracts a networkas one or more network slices, and each network slice includes a seriesof logical network functions, to meet different requirements ofdifferent service types. For example, in a 5th generation (The 5thGeneration, “5G” for short) mobile communications network, networkslicing is an on-demand networking manner, and brings, to an operator, anew service that can be adjusted depending on a continuously changinguser requirement and that can quickly meet a new applicationrequirement.

The network slicing technology abstracts, based on scenariorequirements, a physical infrastructure resource in the 5G network as aplurality of parallel network slice instances that are independent ofeach other. In each network slice instance, based on a requirement of aservice scenario and a service model, a network function is customizedand a corresponding network function is orchestrated. One network sliceinstance may be considered as one instantiated 5G network. In such anetwork structure, an operator can provide a network for a user as aservice, and can freely combine entity networks based on indicators suchas a speed, a capacity, coverage, a latency, reliability, security, andavailability, to meet requirements of different users.

It should be noted that terms such as “network management architecture”,“network system”, and “system” in this specification areinterchangeable. For ease of understanding, some terms in thisspecification are described first.

A network slice (Network slice) is a specific logical network that iscustomized based on a different service requirement on a physical orvirtual network infrastructure. The network slice may be a completenetwork that includes an access network and a core network, can providea telecommunications service, and has a network capability. The networkslice may have one or more of the following characteristics: The accessnetwork may be sliced, or may not be sliced. The access network may beshared by a plurality of network slices.

A network slice instance (Network slice instance, NSI) is a reallyoperating logical network, and can meet a network characteristic orservice requirement. One network slice instance may provide one or moreservices. The network slice instance may be created from a network slicetemplate, or may not be created from a network slice template.

The network slice template is a manner of generating the network sliceinstance, and is used to provide a reference for generating the networkslice instance. The network slice template specifies how the networkslice instance should be generated. For example, the network slicetemplate may indicate which network function a network slice shouldinclude and which key performance indicator (Key Performance Indicators,KPI for short) the network slice should meet. The network slice templatemay define a network function that can provide a communications serviceand a network capability, and a logical expression of a resourcecorresponding to the network function.

FIG. 1A is a schematic architectural diagram of a network systemaccording to an embodiment of the present invention. As shown in FIG.1A, the network system includes at least two network slice instances,for example, a network slice instance A, a network slice instance B, anda network slice instance C. The network slice instance A includes a corenetwork control plane network function used for the network sliceinstance A, a core network user plane network function used for thenetwork slice instance A, a shared control plane function, and an accessnetwork device. The network slice instance B includes a core networkcontrol plane network function used for the network slice instance B, acore network user plane network function used for the network sliceinstance B, the shared control plane function, and the access networkdevice. The network slice instance C includes a core network controlplane network function used for the network slice instance C, a corenetwork user plane network function used for the network slice instanceC, the shared control plane function, and the access network device.These network slice instances may share some control plane functions,and the shared control plane functions are collectively referred to ascommon control network functions (Common Control Network functions, CCNFfor short). The CCNF may include an access and mobility managementfunction (Core Access and Mobility Management Function. AMF for short)and a network slice instance selection function. When UE initiallyaccesses a network or performs a tracking area update (tracking areaupdate, TAU for short), the UE provides slice selection assistanceinformation (network slice selection assistance information, NSSAI), sothat the network selects a slice instance of an access network part anda slice instance of a core network part. The NSSAI may include one or aplurality of session management-slice selection assistance information(session management-network slice selection assistance information,SM-NSSAI). A SM-NSSAI may be used to select a specific slice. TheSM-NSSAI may include a slice/service type (Slice/service type, SST forshort). The SST is used to indicate a particular feature and servicetype of a slice. The SM-NSSAI may further include a slice differentiator(Slice Differentiator, SD for short). The SD may further be used todistinguish between a plurality of network slice instances that have asame SST.

The user equipment may be separately connected to a core network controlplane device and a core network user plane device by using the accessnetwork device. The user equipment may be a device such as a personalcommunications service (English: Personal Communication Service, PCS forshort) phone, a cordless telephone set, a Session Initiation Protocol(English: Session Initial Protocol, SIP for short) phone, a wirelesslocal loop (English: Wireless Local Loop, WLL for short) station, or apersonal digital assistant (English: Personal Digital Assistant, PDA forshort). The user equipment may also be referred to as a system, asubscriber unit (Subscriber Unit), a subscriber station (SubscriberStation), a mobile station (Mobile Station), a mobile station (Mobile),a remote station (Remote Station), an access point (Access Point), aremote terminal (Remote Terminal), an access terminal (Access Terminal),a user terminal (User Terminal), a user agent (User Agent), or aterminal.

Due to a deployment, a network slice is usually available only in aparticular area. The area may be of a cell level, namely, the networkslice is available in one or more cells. Alternatively, the area may beof a tracking area (Tracking Area, TA) level, namely, the network sliceis available in one or more TAs. For example, in a shopping mall, anoperator may deploy a network slice within a range of the shopping mall,to provide a service for a user within the range of the shopping mall.After leaving the shopping mall, the user is not served by the networkslice. FIG. 1B is a schematic diagram in which a network slice isdeployed by area. As shown in FIG. 1B, an access network device supportstwo cells, one cell A supports a network slice instance 1, and the othercell B supports a network slice instance 2. FIG. 1C is another schematicdiagram in which a network slice is deployed by area. As shown in FIG.1C, an access network device gNB1 supports a network slice instance 1and a network slice 2, and another access network device gNB2 supports anetwork slice instance 3. The embodiments of the present inventionintend to resolve a technical problem about how to enable UE to aware anetwork slice instance deployed by area. A solution is that each cell ina network broadcasts a slice instance supported by the cell, forexample, broadcasts information about SM-NSSAI or an ID of the networkslice instance supported by the cell. Another solution is as follows:Dedicated signaling is used to enable the UE to aware the network sliceinstance deployed by area, thereby reducing signaling overheads. Thefollowing uses FIG. 2 , FIG. 3 , and FIG. 7 as examples to describe howthe UE aware the network slice instance deployed by area.

FIG. 2 is a schematic interaction diagram of a service request when userequipment is switched from an idle mode to a connected mode. As shown inFIG. 2 , the service request process includes the following steps:

Step 201. A core network device triggers a paging process. The corenetwork device sends a paging signal to the user equipment by using anaccess network device.

Step 202. The user equipment sends a service request to the accessnetwork device. The access network device sends a service request to thecore network device.

Step 203. The core network device sends an initial context setup requestto the access network device, where the request includes firstinformation. After the access network device receives the initialcontext setup request, the access network device stores the firstinformation.

Step 204. The access network device sends a radio resource control(Radio Resource Control, RRC for short) connection reconfigurationrequest to the user equipment, where the request includes the firstinformation. The user equipment receives the RRC connectionreconfiguration request, and after receiving the first information, theuser equipment may store the first information.

Step 205. The user equipment sends an RRC connection reconfigurationcomplete message to the access network device, and the access networkdevice receives the RRC connection reconfiguration complete message.

Step 206. The access network device sends an initial context setuprequest complete message to the core network device. The core networkdevice receives the initial context setup request complete message.

The core network device may be a network element that includes an accessand mobility management function, for example, an AMF entity.Optionally, before step 202, a random access procedure may be furtherincluded.

In the foregoing service request process, the access network device mayobtain the first information. The first information may include networkslice availability (Slice Availability) information. In an embodiment,the first information includes information about a cell that supports anetwork slice instance and that allows or does not allow the userequipment to access. The first information may also include informationabout a network slice instance that allows being accessed by the userequipment and another network slice instance that allows to be switched.In a case, the network slice instance is determined by using networkslice selection assistance information.

Optionally, the first information may further include information abouta public land mobile network (Public Land Mobile Network, PLMN forshort) that allows or does not allow the UE to access. The firstinformation may further include a data network name (Data Network Name,DNN for short) that allows or does not allow the UE to access.

The first information may be represented in a form of a list or aninformation set. Table 1 shows a first representation form of the firstinformation. Table 1 may include an NSSAI list (NSSAI List). Each NSSAIin the NSSAI list may include the following content: information about acell that allows access, information about a cell that does not allowaccess, and information about NSSAI that allows being switched.Information about each cell may include a PLMN ID and a cell identifier(Cell ID). Each NSSAI may include an NSSAI identifier (NSSAI ID). Table1 may further include DNN information. Specifically, the NSSAI may berepresented by using SM-NSSAI. On an SM-NSSAI granularity basis,differentiated processing and area-based processing may be implementedon different SM-NSSAI in a single network slice instance, and anoperator can flexibly perform slice deployment by area.

TABLE 1 Quantity of Element name elements Element explanation Servingpublic land mobile network SM-NSSAI list A quantity of elements in thelist is M1 >SM-NSSAI ID Includes a slice/service type and a slicedifferentiator >List of cells that A quantity of allow access elementsin the list is N1 >>Public land mobile network ID >>Cell ID >List ofcells that do A quantity of not allow access elements in the list isN2 >>Public land mobile network ID >>Cell ID >List of SM-NSSAI Aquantity of List of SM-NSSAI IDs that that is switchable elements in areallowed to be the list is M2 switched to SM-NSSAI >>ID of allowedIncludes a slice/service type SM-NSSAI and a slice differentiator >Datanetwork name

Table 2 shows a second representation form of the first information.Table 2 may include information about a cell that allows access andinformation about a cell that does not allow access. Each cell thatallows access may include the following content: a PLMN ID, a cell ID,and a corresponding NSSAI list. The NSSAI list may include an NSSAI IDand information about NSSAI that is switchable. Each cell that does notallow access may include the following content: a PLMN ID, a cell ID,and a corresponding NSSAI list. The NSSAI list may include an NSSAI ID.Table 2 may further include DNN information. Specifically, the NSSAI maybe represented by using SM-NSSAI.

TABLE 2 Quantity of Element name elements Element explanation Servingpublic land mobile network List of cells that A quantity of allow accesselements in the list is M1 >Public land mobile network ID >CellID >SM-NSSAI list A quantity of elements in the list is N1 >>SM-NSSAI IDIncludes a slice/service type and a slice differentiator >>List ofSM-NSSAI A quantity of List of SM-NSSAI IDs that that is switchableelements in are allowed to be switched the list is N2 to SM-NSSAI >>>IDof Includes a slice/service type allowed SM-NSSAI and a slicedifferentiator >Data network name List of cells that A quantity of donot allow access elements in the list is M2 >Public land mobile networkID >Cell ID >SM-NSSAI list A quantity of elements in the list isN3 >>SM-NSSAI Includes a slice/service type and a slice differentiator

In another embodiment, the first information includes information abouta tracking area (Tracking area TA for short) that supports a networkslice instance and that allows or does not allow the user equipment toaccess. The first information may further include information indicatingthat a network slice instance accessed by the user equipment is allowedto be switched to another network slice instance. The network sliceinstance is determined by using network slice selection assistanceinformation. Optionally, the first information may further includeinformation about a public land mobile network (Public Land MobileNetwork, PLMN for short) that allows or does not allow the UE to access.The first information may further include information about a DNN thatallows or does not allow the UE to access.

Table 3 shows a third representation form of the first information.Table 3 may include an NSSAI list (NSSAI List). Each NSSAI in the NSSAIlist may include the following content: information about a TA thatallows access, information about a TA that does not allow access, andinformation about NSSAI that is allowed to be switched. Informationabout each TA may include a PLMN ID and a cell identifier (Cell ID).Each NSSAI may include an NSSAI identifier (NSSAI ID). Table 3 mayfurther include DNN information. Specifically, the NSSAI may berepresented by using SM-NSSAI.

TABLE 3 Quantity of Element name elements Element explanation Servingpublic land mobile network SM-NSSAI list A quantity of elements in thelist is M1 >SM-NSSAI ID Includes a slice/service type and a slicedifferentiator >List of tracking areas A quantity of that allow accesselements in the list is N1 >>Public land mobile network ID >>Trackingarea ID >List of tracking areas A quantity of that do not allow elementsin access the list is N2 >>Public land mobile network ID >>Tracking areaID >List of SM-NSSAI A quantity of List of SM-NSSAI IDs that that isswitchable elements in the are allowed to be switched list is M2 toSM-NSSAI >>ID of allowed Includes a slice/service type SM-NSSAI and aslice differentiator >Data network name

Table 4 shows a fourth representation form of the first information.Table 4 may include a tracking area list. The tracking area list mayinclude information about a tracking area that allows access andinformation about a tracking area that does not allow access. Eachtracking area that allows access may include the following content: aPLMN ID, a TA ID, and a corresponding NSSAI list. The NSSAI list mayinclude an NSSAI ID and information about NSSAI that is switchable. Eachtracking area that does not allow access may include the followingcontent: a PLMN ID, a TA ID, and a corresponding NSSAI list. The NSSAIlist may include an NSSAI ID. Specifically, the NSSAI may be representedby using SM-NSSAI.

TABLE 4 Quantity of Element name elements Element explanation Servingpublic land mobile network List of tracking areas A quantity of thatallow access elements in the list is M1 >Public land mobile networkID >Tracking area ID >SM-NSSAI list A quantity of elements in the listis N1 >>SM-NSSAI ID Includes a slice/service type and a slicedifferentiator >>List of SM-NSSAI A quantity of List of SM-NSSAI IDsthat that is switchable elements in are allowed to be switched the listis N2 to SM-NSSAI >>>ID of allowed Includes a slice/service typeSM-NSSAI and a slice differentiator >Data network name List of trackingareas A quantity of that do not allow access elements in the list isM2 >Public land mobile network ID >Tracking area ID >SM-NSSAI list Aquantity of elements in the list is N3 >>SM-NSSAT Includes aslice/service type and a slice differentiator

Table 1 and Table 2 use a cell-based granularity, so that a network hasgood deployment flexibility. Table 3 and Table 4 use a TA-basedgranularity, so that a network slice can be deployed in a larger area.

In Table 1 to Table 4, the network slice instance is determined by usingthe network slice selection assistance information. It should be notedthat the network slice instance may alternatively be determined by usinga network slice instance identifier. This may be implemented byreplacing the NSSAI in Table 1 to Table 4 is correspondingly with thenetwork slice instance (Slice Instance). When the network slice instanceis determined by using the network slice instance identifier, signalingoverheads may be reduced.

Table 5 shows a fifth representation form of the first information.Table 5 is corresponding to Table 1. Table 5 may include a network sliceinstance list (Slice Instance List). Each network slice instance in theslice instance list may include the following content: information abouta cell that allows access, information about a cell that does not allowaccess, and information about a network slice instance that isswitchable. Information about each cell may include a PLMN ID and a cellidentifier (Cell ID). The information about the network slice instancethat is switchable may include an identifier (ID) of the network sliceinstance that is switchable.

TABLE 5 Quantity of Element name elements Element explanation Servingpublic land mobile network Slice ID list A quantity of elements in thelist is M1 >Slice ID Identifier of a slice instance >List of cells thatA quantity of allow access elements in the list is N1 >>PubIic landmobile network ID >>Cell ID >List of cells that do A quantity of notallow access elements in the list is N2 >>Public land mobile networkID >>Cell ID >List of slices that are A quantity of switchable elementsin the list is M2 >>ID of a allowed Identifier of a slice sliceinstance >Data network name

The first information may alternatively be represented by using a RANnotification area (RAN notification area) ID. For example, the cell IDor the tracking area ID is replaced with the RAN notification area ID.

The first information may be referred to as slice-related mobilityinformation. When the first information is represented in a form of atable, the first information may also be referred to as a slice-relatedmobility list, and the first information may be used as a part of a userequipment context. Based on the slice-related mobility list, thefollowing behavior of the UE is decided, for example, the UE is allowedor is not allowed to access a cell, data transmission behavior, orhandover behavior. Using dedicated signaling of the UE ensures that theUE can aware area-based slice deployment, so that signaling overheadsare reduced.

It should be noted that the access network device and the user equipmentmay further obtain the first information by using another procedure, forexample, may obtain the first information by using a procedure in whichthe user equipment accesses (Attach) a network. FIG. 3 is a schematicinteraction diagram in which user equipment accesses a network. The userequipment and an access network device may also obtain first informationby using an attach procedure. As shown in FIG. 3 , that user equipmentaccesses a network specifically includes the following steps:

Step 301. The user equipment sends a network access request to theaccess network device. The access network device sends a network accessrequest to a core network device.

Step 302. The core network device sends an initial context setup requestto the access network device, where the request includes the firstinformation. For description of the first information, refer to theforegoing description. The access network device receives theinformation and stores the first information.

Step 303. The access network device sends an RRC connectionreconfiguration request to the user equipment, where the requestincludes the first information.

Step 304. The user equipment sends an RRC connection reconfigurationcomplete message to the access network device.

Step 305. The access network device sends an initial context setuprequest complete message to the core network device.

Optionally, before step 301, a random access procedure may be furtherincluded.

After obtaining the first information, the user equipment may store thefirst information. For the UE in a various state, some operations areperformed based on the first information. The following describes howthe first information is used for user equipment in various states.

For connected user equipment (connected UE), when the UE is handed over,a serving cell/base station uses the first information as one of factorsto determine a specific cell to which the UE is handed over or aspecific cell, in a specific TA, to which the UE is handed over. Forexample, the access network device uses the first information as one offactors to select a target access network device for the UE. Inaddition, the access network device uses the first information as a partof a user equipment context (UE context), and transfers the firstinformation to the target access network device in a handover process.

FIG. 4A is a schematic diagram of a mobility scenario according to anembodiment of the present invention. As shown in FIG. 4A, an accessnetwork device gNB1 supports a network slice instance #1 and a networkslice instance #2, and an access network device gNB2 supports same typesof network slice instances as the access network device gNB1. However,an access network device gNB3 supports only the network slice instance#1. Alternatively, the access network device gNB1 supports SM-NSSAI #1and SM-NSSAI #2, and the access network device gNB2 also supports theSM-NSSAI #1 and the SM-NSSAI #2, but the access network device gNB3supports only the SM-NSSAI #1.

When other conditions (such as a measurement result reported by UE and aload status) are the same or similar, the access network device gNB1preferably hands over the UE to the access network device gNB2 thatsupports two network slice instances or two SM-NSSAIs. In another case,for example, when the measurement result reported by the UE indicatesthat the gNB3 has best network quality, the gNB1 hands over the UE tothe gNB3. In addition, the gNB1 determines, based on first information,whether the SM-NSSAI #2 supported by the source access network devicegNB1 is allowed to be switched to the SM-NSSAI #1 supported by the gNB3,to use related configurations of the SM-NSSAI #1. If the SM-NSSAI #2 isallowed to be switched to the SM-NSSAI #1, the gNB1 performs switchingfrom the SM-NSSAI #2 to the SM-NSSAI #1, and notifies the UE. Otherwise,the gNB1 refuses a request for switching the SM-NSSAI #2, and notifiesthe UE. Alternatively, the gNB1 determines, based on first information,whether the network slice instance #2 supported by the source accessnetwork device gNB1 is allowed to be switched to the network sliceinstance #1 supported by the gNB3, to use related configurations of thenetwork slice instance #1. If the network slice instance #2 is allowedto be switched to the network slice instance #1, the gNB1 performsswitching from the network slice instance #2 to the network sliceinstance #1, and notifies the UE; or otherwise, the gNB1 refuses arequest for switching the network slice instance #2, and notifies theUE.

FIG. 4B is a schematic interaction diagram in which user equipment ishanded over by using an interface (such as an NG2 interface) between anaccess network device and a core network device. In the handoverprocess, a target access network device may obtain first information,and the user equipment obtains updated first information. As shown inFIG. 4B, the handover process specifically includes the following steps:

Step 401. The user equipment sends a measurement report to an accessnetwork device gNB1.

Step 402. The access network device gNB1 selects a gNB2 as the targetaccess network device of the user equipment based on stored firstinformation of the user equipment, and sends a handover request to thecore network device. Before step 402, the access network device gNB1 andthe access network device gNB2 may exchange information about NSSAI(which may be specifically SM-NSSAI) respectively supported by theaccess network device gNB1 and the access network device gNB2 or IDs ofnetwork slice instances respectively supported by the access networkdevice gNB1 and the access network device gNB2.

Step 403. The core network device sends a handover request to the accessnetwork device gNB2, where the request includes first information.

Step 404. The access network device gNB2 sends a handover requestacknowledgement (Handover Request Ack) to the core network device.

Step 405. The core network device sends a handover command to the accessnetwork device gNB1, where the command includes the first information.

Step 406. The access network device gNB1 sends a handover command to theuser equipment, where the command includes the first information. Thehandover command may be sent by using an RRC connection reconfigurationmessage.

Step 407. The user equipment starts a process of establishing an RRCconnection to the access network device gNB2.

FIG. 5 is a schematic interaction diagram in which user equipment ishanded over by using an interface (such as an Xn interface) betweenaccess network devices. In the handover process, a source access networkdevice gNB1 determines, based on first information, a target basestation to which the user equipment is to be handed over, and transfersthe first information to the target access network device by using theXn interface. As shown in FIG. 5 , the handover process specificallyincludes the following steps:

Step 501. The access network device gNB1 and an access network devicegNB2 exchange information about NSSAI (which may be specificallySM-NSSAI) respectively supported by the access network device gNB1 andthe access network device gNB2 or IDs of network slice instancesrespectively supported by the access network device gNB1 and the accessnetwork device gNB2.

Step 502. The user equipment sends a measurement report to the accessnetwork device gNB1.

Step 503. The access network device gNB1 determines, based on storedfirst information of the user equipment, whether an ongoing sliceservice of the user equipment is allowed to be switched to a sliceinstance supported by the access network device gNB2. If the ongoingslice service is allowed to be switched to the slice instance supportedby the access network device gNB2, selects the gNB2 as the target accessnetwork device of the user equipment, and sends a handover request toaccess network device gNB2. The request includes the first information.

Step 504. The access network device gNB2 sends a handover requestacknowledgement (Handover Request Ack) to the access network devicegNB1.

Step 505. The access network device gNB1 sends a handover command to theuser equipment. The handover command may be sent by using an RRCconnection reconfiguration message.

For connected user equipment, the core network device may furtherdetermine, based on the first information, whether the user equipmentcan roam to another operator.

For inactive (inactive) user equipment, the core network device storesuser equipment context information, and the access network device alsostores the user equipment context information. In a movement process ofthe user equipment, the user equipment takes the first information intoconsideration to determine whether the user equipment can continueperforming data transmission (such as small packet transmission).

When the inactive user equipment moves from coverage of the accessnetwork device gNB1 shown in FIG. 4A to coverage of the access networkdevice gNB2, the user equipment may decide data transmission behavior ofthe user equipment based on the first information. Specifically, whenthe user equipment finds, based on the first information, that theSM-NSSAI #2 is allowed to be switched to the SM-NSSAI #1, the userequipment is handed over from the SM-NSSAI #2 to the SM-NSSAI #1, thatis, uses a configuration parameter of the SM-NSSAI #1 (which includes asame logical channel priority) to continue transmitting a service of theSM-NSSAI #2. Otherwise, the user equipment stops corresponding datatransmission of the SM-NSSAI #2, and continues to transmit a service ofthe SM-NSSAI #1.

When the inactive user equipment moves from the coverage of the accessnetwork device gNB1 in FIG. 4A to the coverage of the access networkdevice gNB2, the access network device may also decide the datatransmission behavior of the user equipment based on the firstinformation. Specifically, the user equipment triggers a statetransition request, and the access network device determines whetherdata of the SM-NSSAI #2 can be switched to the SM-NSSAI #1 fortransmission. FIG. 6 is a schematic interaction diagram of statetransition of inactive user equipment. As shown in FIG. 6 , the statetransition includes the following steps:

Step 601. The user equipment sends an RRC connection resume request toan access network device.

Step 602. The access network device gNB2 sends a user equipment contextobtaining request to an access network device gNB1.

Step 603. The access network device gNB1 sends a user equipment contextobtaining response to the access network device gNB2, where the responseincludes first information. The access network device gNB2 may find,based on the first information, whether an ongoing session of the userequipment that is based on SM-NSSAI #2 can be switched to a session thatis based on SM-NSSAI #1.

Step 604. The access network device gNB2 sends an RRC connection resumeresponse to the user equipment, where the response includes the firstinformation. If it is found, based on the first information, that theuser equipment is allowed to be handed over from the SM-NSSAI #2 to theSM-NSSAI #1, the user equipment uses a configuration parameter (whichincludes a same logical channel priority) of the SM-NSSAI #1 to continuetransmitting a service of the SM-NSSAI #2, or otherwise, the userequipment stops transmitting a service of the SM-NSSAI #2.

Step 605. The user equipment sends an RRC connection resume complete tothe access network device gNB1.

If UE that receives the first information enters an idle mode, the UEalso uses the first information to perform a subsequent operation. Forexample, when the UE performs cell reselection, and the UE finds that ahighest-priority inter-frequency (inter-frequency) cell or ahighest-level intra-frequency (intra-frequency) cell of the UE is a cellthat supports a network slice instance and that does not allow access,the UE cannot use the cell as a candidate cell within a first time T1.After the first time T1 expires, if the UE still cannot select asuitable cell to camp on, the restriction is canceled. When the UE hasleft a slice deployment area for a time period, the UE may delete thefirst information. The UE may further use the first information toattach to a suitable cell, to trigger a service request of a networkslice supported by the cell.

The foregoing uses examples to provide description about obtaining thefirst information by the access network device and the user equipment.It should be noted that the access network device and the user equipmentmay obtain the first information in another manner. For example, for theconnected UE, the core network device also notifies a serving (serving)access network device of the first information through context setup,S1/X2 handover, and sending of NAS downlink signaling. In a trackingarea update procedure of the user equipment, the UE and the accessnetwork device may also obtain the first information. The UE may alsoobtain the first information by using an RRC connection release message,so that the UE is redirected to a cell that supports NSSAI or a networkslice instance ID.

FIG. 7 is a schematic diagram of a tracking area update procedure ofuser equipment. As shown in FIG. 7 , the procedure includes thefollowing steps:

Step 701. The user equipment sends a tracking area update request to anaccess network device. The access network device sends the tracking areaupdate request to a core network device.

Step 702. The core network device sends a tracking area update responseto the access network device, where the response includes firstinformation. The access network device stores the first information.

Step 703. The access network device sends a tracking area updateresponse to the user equipment, where the response includes the firstinformation.

Step 704. The UE sends a tracking area update complete message to theaccess network device. The access network device sends a tracking areaupdate complete message to the core network device.

In the foregoing description, the access network device and the UEobtain the first information by using dedicated signaling of the UE, sothat signaling overheads can be reduced. It should be noted that thefirst information may be broadcast, so that the UE obtains the firstinformation. In this case, the first information may include informationabout NSSAI that is supported or not supported by a cell or an ID of anetwork slice instance that is supported or not supported by the cell,and further includes information about NSSAI that is supported or notsupported by another cell or an ID of a network slice instance that issupported or not supported by the another cell. Alternatively, the firstinformation may include information about NSSAI that is supported or notsupported by a tracking area level or an ID of a network slice instancethat is supported or not supported by the tracking area level, andfurther includes information about NSSAI that is supported or notsupported by another tracking area level or an ID of a network sliceinstance that is supported or not supported by the another tracking arealevel.

In the embodiments of the present invention, the access network deviceand the user equipment may obtain the first information. By using thefirst information, idle UE can select a suitable cell to camp on anetwork, so that the UE can attach to a cell that supports a networkslice instance. Connected UE can be handed over to a suitable targetcell; and inactive UE can continue transmitting data in a target cell ofthe UE. Therefore, impact of area-based slice deployment on the UE andthe network can be avoided. In this way, the UE can better awarearea-based network deployment, a slice is visible to the UE, unnecessarycell access, handover, roaming, and the like are avoided, and UEexperience is improved.

With reference to FIG. 1 to FIG. 7 , the foregoing describes in detailthe communication method according to the embodiments of the presentinvention. With reference to FIG. 8 to FIG. 10 , the following describesin detail an access network device, user equipment, and a core networkdevice according to the embodiments of the present invention.

FIG. 8 is a schematic diagram of an access network device according toan embodiment of the present invention. The access network deviceincludes a processor 810, a transceiver 820, and a memory 830. Theprocessor 810 is separately connected to the transceiver 820 and thememory 830. The memory 830 is configured to store an instruction. Theprocessor 810 is configured to execute the instruction stored in thememory 830, to control the transceiver 820 to send a signal and/orreceive a signal. Specifically, the processor 810 may control thetransceiver 820 to perform receiving and sending steps performed by theaccess network device in the embodiments shown in FIG. 2 to FIG. 7 . Fordetails, refer to a corresponding process in the foregoing methodembodiments. Details are not described herein again.

FIG. 9 is a schematic diagram of user equipment according to anembodiment of the present invention. The user equipment includes aprocessor 910, a transceiver 920, and a memory 930. The processor 910 isseparately connected to the transceiver 920 and the memory 930. Thememory 930 is configured to store an instruction. The processor 910 isconfigured to execute the instruction stored in the memory 930, tocontrol the transceiver 920 to send a signal and/or receive a signal.Specifically, the processor 910 may control the transceiver 920 toperform receiving and sending steps performed by the user equipment inthe embodiments shown in FIG. 2 to FIG. 7 . The processor 910 maycontrol the memory 930 to store first information. For details, refer toa corresponding process in the foregoing method embodiments. Details arenot described herein again.

FIG. 10 is a schematic diagram of a core network device according to anembodiment of the present invention. The core network device includes aprocessor 1010, a transceiver 1020, and a memory 1030. The processor1010 is separately connected to the transceiver 1020 and the memory1030. The memory 1030 is configured to store an instruction. Theprocessor 1010 is configured to execute the instruction stored in thememory 1030, to control the transceiver 1020 to send a signal and/orreceive a signal. Specifically, the processor 1010 may control thetransceiver 1020 to perform receiving and sending steps performed by thecore network device in the embodiments shown in FIG. 2 to FIG. 7 . Fordetails, refer to a corresponding process in the foregoing methodembodiments. Details are not described herein again.

It should be understood that sequence numbers of the foregoing processesdo not mean execution sequences in the embodiments of the presentinvention. The execution sequences of the processes should be determinedbased on functions and internal logic of the processes, and should notbe construed as any limitation on the implementation processes of theembodiments of the present invention.

A person of ordinary skill in the art may be aware that units andalgorithm steps in the examples described with reference to theembodiments disclosed in this specification may be implemented byelectronic hardware, computer software, or a combination thereof. Toclearly describe the interchangeability between the hardware and thesoftware, the foregoing has generally described compositions and stepsof each example based on functions. Whether the functions are performedby hardware or software depends on particular applications and designconstraint conditions of the technical solutions. A person skilled inthe art may use different methods to implement the described functionsfor each particular application, but it should not be considered thatthe implementation goes beyond the scope of the present invention.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is only an example. For example, the unit division is onlylogical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the shown or discussed mutualcouplings or direct couplings or communication connections may beimplemented through some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electrical, mechanical, or other forms.

All or some of the foregoing embodiments may be implemented by usingsoftware, hardware, firmware, or any combination thereof. When softwareis used to implement the embodiments, all or some of the embodiments maybe implemented in a form of a computer program product. The computerprogram product includes one or more computer instructions. When thecomputer program instructions are loaded and executed on a computer, allor some of the procedures or functions according to the embodiments ofthe present invention are generated. The computer may be ageneral-purpose computer, a dedicated computer, a computer network, oranother programmable apparatus. The computer instructions may be storedin a computer-readable storage medium or may be transmitted from acomputer-readable storage medium to another computer-readable storagemedium. For example, the computer instructions may be transmitted from awebsite, computer, server, or data center to another website, computer,server, or data center in a wired (for example, a coaxial cable, anoptical fiber, or a digital subscriber line (DSL)) or wireless (forexample, infrared, radio, or microwave) manner. The computer-readablestorage medium may be any usable medium accessible by a computer, or adata storage device, such as a server or a data center, integrating oneor more usable media. The usable medium may be a magnetic medium (forexample, a floppy disk, a hard disk, or a magnetic tape), an opticalmedium (for example, a DVD), a semiconductor medium (for example, asolid state disk Solid State Disk (SSD)), or the like.

To make the application document brief and clear, the foregoingtechnical features and descriptions in an embodiment may be consideredto be applicable to other embodiments, and are not described in otherembodiments again.

The foregoing descriptions are only specific implementations of thepresent invention, but are not intended to limit the protection scope ofthe present invention. Any modification or replacement readily figuredout by a person skilled in the art within the technical scope disclosedin the present invention shall fall within the protection scope of thepresent invention. Therefore, the protection scope of the presentinvention shall be subject to the protection scope of the claims.

What is claimed is:
 1. A communication method, comprising: sending, by acore network device, a handover request to a target access networkdevice, wherein the handover request comprises first information, andthe first information comprises an identifier of allowed sessionmanagement-network slice selection assistance information (NSSAI);wherein the session management-NSSAI comprises a slice/service type; andreceiving, by the core network device, a handover requestacknowledgement sent by the target access network device.
 2. Thecommunication method according to claim 1, wherein the target accessnetwork device is selected as handover target by a source access networkdevice serving a user equipment undergoing handover.
 3. Thecommunication method according to claim 1, wherein the first informationfurther comprises information about a tracking area that allows a userequipment to access.
 4. The communication method according to claim 1,wherein the first information further comprises information about atracking area that does not allow a user equipment to access.
 5. Thecommunication method according to claim 1, wherein the first informationfurther comprises information about a public land mobile network thatallows a user equipment to access.
 6. The communication method accordingto claim 5, wherein the session management-NSSAI further comprises aslice differentiator.
 7. The communication method according to claim 1,wherein the session management-NSSAI is used to select a specific slice.8. The communication method according to claim 1, further comprising:after receiving, by the core network device, a handover requestacknowledgement sent by the target access network device, sending, bythe core network device, a handover command to a source access networkdevice.
 9. A core network device, comprising: a transceiver; at leastone processor; and one or more memories connected to the at least oneprocessor and storing programming instructions for execution by the atleast one processor to cause the core network device to performoperations comprising: sending, by using the transceiver, a handoverrequest to a target access network device, wherein the handover requestcomprises first information, and the first information comprises anidentifier of allowed session management-network slice selectionassistance information (NSSAI); wherein the session management-NSSAIcomprises a slice/service type; and receiving, by using the transceiver,a handover request acknowledgement sent by the target access networkdevice.
 10. The core network device according to claim 9, wherein thetarget access network device is selected as handover target by a sourceaccess network device serving a user equipment undergoing handover. 11.The core network device according to claim 9, wherein the firstinformation further comprises information about a tracking area thatallows a user equipment to access.
 12. The core network device accordingto claim 9, wherein the first information further comprises informationabout a tracking area that does not allow a user equipment to access.13. The core network device according to claim 9, wherein the firstinformation further comprises information about a public land mobilenetwork that allows a user equipment to access.
 14. The core networkdevice according to claim 13, wherein the session management-NSSAIfurther comprises a slice differentiator.
 15. The core network deviceaccording to claim 9, wherein the session management-NSSAI is used toselect a specific slice.
 16. The core network device according to claim9, wherein the operations comprise: after receiving, by using thetransceiver, a handover request acknowledgement sent by the targetaccess network device, sending, by using the transceiver, a handovercommand to a source access network device.
 17. A communication system,comprising: a core network device and an access network device; the corenetwork device is configured to send a handover request to the accessnetwork device, wherein the handover request comprises firstinformation, and the first information comprises an identifier ofallowed session management-network slice selection assistanceinformation (NSSAI); wherein the session management-NSSAI comprises aslice/service type; and the access network device is configured to senda handover request acknowledgement to the core network device.
 18. Thecommunication system according to claim 17, wherein the firstinformation further comprises information about a tracking area thatallows user equipment to access.
 19. The communication system accordingto claim 17, wherein the first information further comprises informationabout a public land mobile network that allows a user equipment toaccess.
 20. The communication system according to claim 17, wherein thesession management-NSSAI further comprises a slice differentiator.